Taste cue. 1. An amino acid used to enhance flavors and add a pleasant meaty taste to food products. 2. The fifth basic taste--MSG--called umami by the Japanese. 3. A flavor additive which prompts food items to "speak" to the tongue as "meats."

Usage: With a rich "meaty" flavor, glutamate is a frequent additive to edible consumer products such as crackers, chips, seasonings, soup bases, sauces, and "natural flavorings." Rich in free glutamate, parmesan cheese and tomatoes, e.g., appeal to the tongues of carnivores.

History. MSG dates back to Oriental antiquity, to sea tangle, a seaweed used to make stock. Unknown in Europe until the 16th century, the New World's tomato, combined with onions and olive oil by Spanish chefs, has become a main ingredient of soups, sauces, pastes, and juices. (N.B.: Malay kaychup evolved as catsup in England, and was mass-marketed as a consumer product in the U.S. by the H.J. Heinz Co. in 1876.)

Chemistry. High levels of free glutamate (a building block of protein) are found in mushrooms, tomatoes, and peas. Hydrolyzed vegetable protein breaks into glutamic acid, which turns into the white crystalline flavor enhancer, monosodium glutamate (MSG): COOH(CH2)2CH(NH2)COONa.

Neuro-note. A study of the gustofacial reflex of newborns (as young as 24 hours in age) found a. that unseasoned soup stock produced an aversion response, but that b. soup seasoned with MSG produced an acceptance response (National Food Safety 1987).